Replacing saturated animal fats with polyunsaturated fats rich in omega-6 linoleic acid may not be beneficial for heart patients, researchers have claimed. Linoleic acid is present in high amounts in some commonly used vegetable oils such as corn, sunflower, safflower and soybean.

Swapping saturated fats like butter or lard for polyunsaturated vegetable oils and spreads made from them is a common suggestion for those looking to switch to a heart healthy diet.

Researchers recovered missing data from the Sydney Diet Heart Study in the 1960s. The trial involved 458 men aged 30-59 years who had suffered a heart attack or an episode of angina.

Using modern statistical methods to compare death rates, researchers concluded that there was no evidence of the benefit of replacing saturated fats with omega-6 linoleic acid in this group of people, and actually a possible increased risk of cardiovascular disease.

Victoria Taylor, Senior Dietitian at the British Heart Foundation (BHF), said: “Our understanding of the effect of different fats on our heart develops all the time as new research into this complex issue is published.

“Replacing saturated fats with unsaturated alternatives is a well-known recommendation for your heart, which is based on many large and in-depth studies. However, this research highlights the need for us to further understand how different unsaturated fats affect our risk of heart disease.

“Whichever fats you use it’s important to be sparing with them. Try to grill, bake, or steam your food, rather than frying. Measuring out oils instead of pouring straight from the bottle is another good way of making sure you’re not overdoing it.”